Marine scientists are calling on New Zealand to close fisheries which are home to the world's rarest dolphin, also known as "the hobbit of the sea".

The International Whaling Commission's (IWC) scientific committee says only a few dozen Maui's dolphins remain and immediate action is needed to prevent their extinction.

The critically endangered dolphin is only found in shallow waters off the North Island's west coast.

The committee says it fears fishing may wipe out the remaining population.

"It is of the highest priority to take immediate management actions that will eliminate by-catch of Maui's dolphins," it said in a report published today.

"This includes full closure of any fisheries within the range of Maui's dolphins that are known to pose a risk."

Maui dolphin named after Polynesian demigod

The grey and white Maui's, named after a Polynesian demigod, is one of the world's smallest dolphins, with a maximum length of 1.7 metres.

An estimated three to four dolphins are accidentally killed as by-catch every year, a loss the IWC report says is unsustainable in a population of about 50 adults.

The report, which summarises the finding of an IWC scientific committee meeting held in Slovenia last month, notes New Zealand has made efforts to save the creature.

"The current management situation falls short of that required to reverse the Maui's dolphin's decline," the report read.

It is the third year in a row the IWC committee, which is made up of more than 200 marine scientists, called for urgent action to save the dolphin.

This time the body asked Wellington to provide it with an annual progress report so it can assess what is being done.

Conservation group NABU International says the request amounts to a rap on the knuckles.

"I think the scientific community has really fallen out of love with New Zealand over this issue," said Barbara Maas, an endangered species specialist with NABU.

Associate Professor of zoology at Otago University Liz Slooten said it was difficult for New Zealand to lecture Japan about its whaling program when it was doing so little to save the Maui's dolphin, despite ample scientific advice on the need to act.

"It's hard to believe that in a country like New Zealand we are taking such a long time to save a dolphin that's only found in our waters," Associate Professor Slooten said.

"The international community is waiting for NZ to do the right thing - it's become really urgent now."